The changes of relative position of the aorta after posterior instrumentation in adolescent idiopathic thoracic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Aorta  Pedicle screw  Position

English Abstract:

  【Abstract】 Objectives: To evaluate the relative spatial position between the aorta and the vertebral body in pre-operation, one-week post-operation and 2 years post-operation in adolescent idiopathic thoracic scoliosis (AIS). Methods: All 22 AIS patients with right-sided major thoracic curve who received posterior correction and instrumentation with pedicle screw construct were included in this study. The position of the aorta and the apical vertebral rotational deformity was evaluated by the measurement of the following parameters in three-dimensional reconstructed CT: aorta-vertebral distance, aorta-vertebral angle, aorta-spinal canal distance, left pedicle screw length and the apical vertebral axial rotational angle (AVR). Cobb angle and thoracic kyphosis were measured in the X-ray film. Results: The mean Cobb angle was corrected from 57.5°±9.8° to 13.6°±6.5° after surgery and settled at 16.2°±6.8° at 2 years follow-up. The correction rate of the major thoracic curve was 77.5% after operation and 73.3% in 2 years follow-up. AVR was also corrected from 29.4°±9.3° to 14.6°±6.9° after surgery. The figure rebounded slightly to 17.4°±6.8° at 2 years follow-up with a correction rate of 49.5% after surgery and 39.7% at 2 years follow-up. For the region between T6 and T11, the measured aorta-vertebral distances were significantly longer as compared to one week after surgery. Correspondingly, the distances measured from T7-T9 segment at 2 years follow-up were also significantly longer than those measured one week after surgery(P<0.05). As far as the aorta-vertebral angle is concerned, the measurements taken from T5-T11 segment prior to surgery were significantly greater than those taken one week afterward. For T7-T10 segment, the aorta-vertebral angles measured at 2 years follow-up were significantly higher than one week after surgery(P<0.05). With regard to the aorta-spinal canal distances, the pre-operational values of T7-T11 segment, were significantly shorter than those one week after surgery. For T6-T10 segment, the aorta-spinal canal distances at 2 years follow-up were significantly shorter in comparison to the earlier measurements taken one week after surgery(P<0.05). Conclusions: In right-sided major thoracic curve AIS patients, the aorta moved anteromedially relative to the spine after posterior correction and instrumentation, while in the 2 years follow-up, the aorta moved posterolaterally. In the treatment of AIS with posterior pedicle screw construct, it was essential to evade the penetration of anterior vertebral cortex or pedicle later cortex by pedicle screw which may cause aorta injury.